Field of the Invention
The present invention relates to a technique to prevent erroneous detection due to a stationary object in human body detection using a range sensor, such as an ultrasonic sensor.
Description of the Related Art
In recent years, in many electronic apparatuses, such as a printer, a human sensor function to determine whether a person is a user or a passerby by measuring the distance from the electronic apparatus to the human body is mounted. As a sensor to implement this human sensor function, for example, an ultrasonic sensor is used (see Japanese Patent Laid-Open No. 2015-195548).
The ultrasonic sensor is a sensor that detects an object by radiating an ultrasonic wave and receiving a reflected wave that returns. By measuring the elapsed time between the ultrasonic wave being output and the reflected wave from the object being received, the distance to the object is calculated. However, the ultrasonic wave that is radiated from the ultrasonic sensor is also reflected by an object other than the human body, which exists on the periphery of the human body. Consequently, unless some measure is taken, there is a possibility that, for example, it is erroneously determined that a user still remains there by the reflected wave from a stationary object, such as a pillar on its periphery and temporarily placed baggage, despite that the user has already left an electronic apparatus, such as a printer. Because of this, it is important to make it possible to distinguish the received reflected wave from a stationary object from that from a human body. Then, the problem of erroneous determination due to a stationary object is a problem common to the all kinds of range sensor.
An object of the present invention is to accurately detect a person who is approaching (or a person who is leaving) an electronic apparatus, such as a printer, by preventing erroneous detection due to a stationary object in human body detection using a range sensor.